We purchased a full fare first class ticket from Unite 1-22-17. HNL to JAC, JAC to DEN and DEN to HNL. Total fare cost for 2 was $3600+ USD. Trip took place last month. When we tried to check in online on 6/12/17, we could not as they split our reservation and bumped us to coach. I am a Million Mile (1.4 million miles) flier that doesn't matter anymore. We called Customer Service and they basically said, "tough luck! and try fixing it at the Jackson Hole airport." That didn't work so we sat in coach. Upon returning home on 6-22 I wrote United Customer Service and sent them a new fare showing the difference in cost between first class and coach was $550 USD each. They wrote back, we will refund $150 each. How can they get away with such thievery with their best customers. After flying exclusively with them and partners for 34 years, we are finished and moving onto other airlines. Disgusted!